A few of my own thoughts. Create yourself a price list that details out your fees, i.e., printed page using premade design - $5.00, printed page using custom-design $10.00, 1 hour design time - $20.00. By doing this you will also have a good idea what to charge for a 20-page printed album whether it is "custom" or "premade". Be sure to include your material costs into your album price (i.e., album cover, slipcovers for pages, embossing on front cover, etc.)
Whatever the amounts are you plug in, showing your customers a price list helps them make informed decisions on what to purchase, but also educates them a bit on what is involved in building your "fee" for a total album. Even if all you did is design the page and give to them to take to print, they are going to be around $5 to get a 12x12 printed, so in essence they received all your time and talents for free.
I think having a price list also helps with the emotional aspect of having to tell someone what you charge. You can provide them with a price list and explain to them the different fees involved that make up your total cost per album. Maybe you incent your previous customers with a discount for any future referrals (20% of their next album at the new rates), but you start charging your new rates to anyone new requesting your services.
The good news for you is you have already earned a reputation based on your work, the unique service you provide, and have clients wanting to buy your services. Let me tell you that is the HARD part of starting any small business. Now start educating them on what they are really buying and getting for their money and start charging them accordingly. They could not go anywhere else and get this done for the price you are charging -- NO WHERE, I promise you. I think you have a new career in the wings, my dear. Post and let us know how it goes

and most of all good luck in your venture.